This present application relates to hot gas path sealing configurations in gas turbine engines. More specifically, but not by way of limitation, the present application relates to the seal formed between the outer radial tip of rotor blade and the surrounding stationary structure.
Generally, combustion or gas turbine engines (hereinafter “gas turbines”) include compressor and turbine sections in which rows of blades are axially stacked in stages. Each stage typically includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central turbine axis or shaft. In operation, generally, the compressor rotor blades are rotated about the shaft, and, acting in concert with the stator blades, compress a flow of air. This supply of compressed air is used within a combustor to combust a supply of fuel. The resulting flow of hot expanding combustion gases, which is often referred to as working fluid, is then expanded through the turbine section of the engine, wherein it is redirected by the stator blades onto the rotor blades so to induce rotation. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft. In this manner, the energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, so to produce the supply of compressed air needed for combustion, as well as, for example, the coils of a generator so to generate electrical power. During operation, however, leakage across the rows of turbine blades negatively impacts engine efficiency.
Many industrial applications, such as those involving power generation and aviation, still rely heavily on gas turbines, and because of this, the engineering of more efficient engines remains an ongoing and important objective. As will be appreciated, even incremental advances in machine performance, efficiency, or cost-effectiveness are meaningful in the highly competitive markets that have evolved around this technology. While there are several known strategies for improving the efficiency of gas turbines, such as, for example, increasing the size of the engine, firing temperatures, or rotational velocities, each of these generally places additional strain on those already highly stressed hot-gas path components. Another manner by which gas turbine engine efficiency may be enhanced is through improved sealing technology, particular relating to the seals formed within the gaps defined between stationary and rotating structure within the gas turbine. As will be appreciated, during operation, working fluid that flows between the outer radial tip of the rotor blade and the surrounding stationary structure represents leakage that negatively impacts efficiency. As a result, there remains a need for improved apparatus, systems, and methods that reduce or eliminate such leakage flows.